1. Field of the Invention
This invention relates to novel azetidine derivatives, and more specifically to azetidine derivatives represented by the following formula (I), ##STR2## wherein R represents a hydrogen atom or a hydroxyl group, and R.sub.a, R.sub.b, R.sub.c, R.sub.a ', R.sub.b ' and R.sub.c ' are identical or different and each represent a lower alkyl group. Further, the invention is concerned with a process for producing such azetidine derivatives.
2. Description of the Prior Art
Carbapenem compounds have in recent years come into the limelight by reason of the fact that thienamycin discovered from the natural world exhibits strong antibacterial activity and .beta.-lactamase inhibitory effect (see Japanese Laid-Open Application No. 73191/1976). In fact, this leads to subsequent publication of numerous compounds analogous to such carbapenem compounds. However, these compounds are all unstable and induce low productivity when produced by fermentation, and hence, are still far from actually useful.
With the foregoing difficulties of the existing techniques in view, the present inventors have carried out extensive study with a view toward preparing compounds of the above-described type by synthesis. As a result, they have succeeded in synthesizing novel .beta.-lactam compounds having antibacterial activities and represented by the following formula (II), ##STR3## wherein A means an alkyl group, aryl group, residual group of a heterocyclic ring or the like.